Worldwide development production of new abiotic-stress-resistant cultivars, i.e., those resistant to such stress conditions as drought, extreme temperatures, or salinity, is on the rise, owing to the expansion of agriculture into previously uncultivated areas. Such areas often suffer from low soil fertility, groundwater of variable salinity, sensitivity to water-logging, deterioration of irrigation-water quality, and irrigation with marginal water with high chloride concentrations. The threat of global warming and the associated fluctuations in weather conditions and precipitation levels are expected to accelerate the expansion of agriculture into previously uncultivated areas.
A major and immediate response of many plant species to abiotic stresses is a decrease in growth rate, which eventually leads to a significant decrease in yield. Among the reasons for the reduction in growth rate under abiotic stresses is a decrease in root conductivity, which induces abrupt stomatal closure, leading to decreased rates of transpiration and photosynthesis. Plants are able to cope with abiotic stresses using a variety of stress-defense mechanisms, such as osmotic regulation, antioxidant protection and ion-homeostasis mechanisms, among others. These mechanisms enable plants to complete their life cycle while maintaining some level of yield, even under stress conditions.
Two main approaches have been to cope with theses problem by producing new stress-resistant cultivars. The first is genetic engineering, using various candidate genes, and the second is classical breeding. However, assessing a plants yield under stress conditions is difficult under field conditions because of the spatial variability in the filed of the soil, soil and moisture conditions, salinity, and light intensity.